The present invention relates to a composite detector used in a fire alarm system or the like.
Some conventional fire detectors used in fire alarm systems independently detect at least two of the environmental parameters heat, light, smoke, and a combustible gas, add or multiply detected analog signals to or with each other, and generate fire alarm signals when the sums or products thereof exceed predetermined values, as described in Japanese Utility Model Publication No. 58-3189 (Fire Detector) and Japanese Patent Disclosure No. 54-77193 (Smoke Detector).
As described above, a fire alarm signal is output only if a value derived from outputs from different types of sensors in the conventional fire detector exceeds a predetermined value. A receiver (central monitor) automatically alarms or displays the fire alarm signal. With this function, the receiver cannot detect the type of signal received. In other words, the receiver cannot discriminate which one of the parameters heat, light and the like is detected according to analog signals from the sensors.